Techniques to drill and complete oil and gas wells below ocean surfaces have been used since the 1950's. Initially, divers were used to set and align well head equipment, because divers can perform these operations in shallow waters. In recent years, production of oil and gas from fields beyond depths at which divers can function has required development of methods to complete wells without the use of divers. U.S. Pat. No. 3,373,807 discloses such a method to connect an underwater pipeline to a submerged wellhead. This method utilizes guidelines to provide guidance and alignment of connectors to the wellhead. A plurality of guidelines are used to orient a flowline including an end connection. The flowline is lowered vertically from a surface ship, and hinges over to a horizontal position after the flowline end connection comes to rest adjacent to the wellhead. A "christmas tree" which connects the flowline end connection to the wellhead is then lowered along the guidelines.
Methods that utilize guidelines are useful in installing sea floor equipment, but are not preferred in waters deeper than about 3,000 feet. In water deeper than this, the guidelines become exceedingly long, heavy and difficult to work with and failure of the long guidelines can cause serious problems. A method to connect a pipeline or flowline bundle to a deep water well without is disclosed in U.S. Pat. No. 4,541,753. This method utilizes a funnel-shaped receiver attached to the subsea wellhead structure to guide a mating stab connected to the flowline end connection. The flowline is lowered vertically from a surface vessel and the position of the surface vessel is adjusted to result in the stab being lowered into the funnel-shaped receiver. The flowline is pivotably mounted to the stab so that it can be laid down on the ocean floor resulting in the end connection rotating to a position relative to the wellhead that had been predetermined. Another receiver funnel attached to the wellhead could then be utilized to guide a christmas tree with means to connect the wellhead to the flowline connection. This christmas tree can be lowered also without a guideline from a surface vessel in a manner similar to the lowering of the flowline end connection.
The methods of patent '753 can be utilized to connect single pipelines or pipe bundles to subsea facilities in water too deep for either divers or guidelines. However, it is also often useful to connect flowlines between wellheads and a central gathering facility in close proximity to each other. Extending single flowlines from a plurality of satellite wellheads to a central production facility is therefore advantageous. Such satellite well clusters used in shallow waters are disclosed in, for example, Ocean Industry, "Saga Plans Subsea Manifold Plus Satellites for Tordis", p. 19, Vol. 26, No. 9, (Nov. 1991). In "Subsea-Completed Wells Account for 18% of Offshore Production", Offshore, by Derrick Booth, p 34-36 (Nov. 1991), Petrobras is credited with having developed "guidelineless drilling and completion hardware" although how this is accomplished is not discussed.
It is therefore desirable to have a method to connect subsea flowlines wherein neither guidelines nor divers are required to perform the connections. It is an object of the present invention to provide such a method.